The invention relates to a sensor apparatus for a self-propelled floor cleaning appliance for detecting a down step with a transmission unit for emitting infrared radiation and a reception unit for receiving infrared radiation and with evaluation electronics for evaluating the intensity of the radiation received.
Moreover, the invention relates to a self-propelled and self-steering floor cleaning appliance having a chassis and an electrical drive unit with electrical control unit and drive wheels mounted on the chassis, and with a sensor apparatus of this type.
A floor surface can be cleaned with the aid of self-propelled and self-steering floor cleaning appliances without the need for an operator. The floor cleaning appliance is in this case moved along the floor surface that is to be cleaned. If it encounters an obstacle, it changes its direction of movement in accordance with a predeterminable control program. To detect a steep downslope on the floor surface or also a step, the floor cleaning appliance is equipped with a sensor apparatus which detects the floor surface that is to be cleaned by means of infrared radiation and forms a proximity sensor which provides an electrical control signal for the control electronics. If the detected distance exceeds a predetermined maximum permissible distance, the floor cleaning appliance likewise executes a change in the direction of movement. To check the distance, the sensor apparatus has a transmission unit which directs infrared radiation onto the floor surface. The infrared radiation which is reflected from the floor surface is received by the reception unit, and the intensity of the reflected radiation is evaluated by the evaluation electronics.
Sensor apparatuses of this type have the difficulty that the intensity of the reflected infrared radiation is dependent not only on the distance between the sensor apparatus and the floor surface, but also on the direction of the radiation reflected from the floor surface. If the floor surface has regions with a reflection surface oriented obliquely with respect to the sensor apparatus, for example in the form of cables or beveled edge regions of floor tiles, the infrared radiation emitted is reflected in a direction away from the reception unit, so that a signal of weak intensity is received even when the true distance is only relatively short.
It has already been proposed to use a position-dependent reception unit, in which case it is not the intensity of the reflected radiation that is evaluated, but rather the point of impingement of the infrared radiation on the reception unit. This point of impingement is dependent on the distance between the sensor apparatus and the floor surface that is to be cleaned. However, position-dependent sensor apparatuses of this type are characterized by considerable production difficulties and are therefore associated with by no means insignificant production costs.
It is an object of the present invention to develop a sensor apparatus and a floor cleaning appliance of the type described in the introduction in such a manner that a down step or a steep downslope in the floor surface can be detected more reliably, and the sensor apparatus can be produced at low cost.